<!DOCTYPE html>
<html lang="zh-CN">

<head>
  <meta charset="UTF-8" />
  <title>京东商城</title>
  <style>
    * {
      margin: 0;
      padding: 0;
      list-style: none;
    }

    .slider {
      height: 340px;
      width: 790px;
      margin: 100px auto;
      position: relative;
    }

    .slider li {
      position: absolute;
      display: none;
    }

    .slider li:first-child {
      display: block;
    }

    .arrow {
      display: none;
    }

    .slider:hover .arrow {
      display: block;
    }

    .arrow-left,
    .arrow-right {
      font-family: "SimSun", "宋体";
      width: 30px;
      height: 60px;
      background-color: rgba(0, 0, 0, 0.1);
      position: absolute;
      top: 50%;
      margin-top: -30px;
      cursor: pointer;
      text-align: center;
      line-height: 60px;
      color: #fff;
      font-weight: 700;
      font-size: 30px;
    }

    .arrow-left:hover,
    .arrow-right:hover {
      background-color: rgba(0, 0, 0, 0.5);
    }

    .arrow-left {
      left: 0;
    }

    .arrow-right {
      right: 0;
    }
  </style>
</head>

<body>
  <div class="slider">
    <ul>
      <li>
        <a href="#"><img src="images/1.jpg" alt="" /></a>
      </li>
      <li>
        <a href="#"><img src="images/2.jpg" alt="" /></a>
      </li>
      <li>
        <a href="#"><img src="images/3.jpg" alt="" /></a>
      </li>
      <li>
        <a href="#"><img src="images/4.jpg" alt="" /></a>
      </li>
      <li>
        <a href="#"><img src="images/5.jpg" alt="" /></a>
      </li>
      <li>
        <a href="#"><img src="images/6.jpg" alt="" /></a>
      </li>
      <li>
        <a href="#"><img src="images/7.jpg" alt="" /></a>
      </li>
      <li>
        <a href="#"><img src="images/8.jpg" alt="" /></a>
      </li>
    </ul>
    <!--箭头-->
    <div class="arrow">
      <span class="arrow-left">&lt;</span>
      <span class="arrow-right">&gt;</span>
    </div>
  </div>

  <script src="./jquery-1.12.4.js"></script>
  <script>
    $(function () {
      // 定义下标
      let index = 0;

      // 右边的箭头
      $(".arrow-right").click(function () {
        index++;

        // 临界点的判断
        if (index === $(".slider>ul>li").length) {
          index = 0;
        }

        $(".slider>ul>li").eq(index).fadeIn().siblings().fadeOut();
      })

      // 左边的箭头
      $(".arrow-left").click(function () {

        index--;

        if (index < 0) {
          // 回到最后一张
          index = $(".slider>ul>li").length - 1;
        }

        $(".slider>ul>li").eq(index).fadeIn().siblings().fadeOut();
      })

      // 自动播放  每间隔一段时间 自动展示下一张
      let timeId = setInterval(function () {
        // $(".arrow-right").click()
        $(".arrow-right").trigger('click')
      }, 1000)

      // 补全：鼠标经过和离开做的事情
      $('ul').on('mouseenter', function () {
        clearInterval(timeId)
      })
      $('ul').on('mouseleave', function () {
        timeId = setInterval(function () {
          // $(".arrow-right").click()
          $(".arrow-right").trigger('click')
        }, 1000)
      })




    });
  </script>
</body>

</html>